[callesgg]

You or your neighbour probably have some cheap chinese device that puts out high frequency noice on the power line.

Either you get rid of that device or you buy something like this: https://www.google.com/search?q=apple+grounded+extention+cab...

[bilekas]

Unless you're running some serious industrial level machinery, home devices have nothing to do with power line noise. It's cause by the air around the lines and the condition of the lines themselves.

[callesgg]

I think you are talking about another type of power line noise.

I am pretty sure a bad switch mode power supply, can push out some nasty stuff.